Although the majority of them are one-dimensionally genocidal, megalomaniacal, and in some cases (such as Cronus, and, to a lesser extent, Ra) apparently barely self-aware (living out the patterns of their behavior as they existed thousands of years ago), there were a few exceptions. Apophis at times showed an unusual amount of insight, lucidity, and tenacity for a Goa'uld, showing great resourcefulness in escaping from Sokar's imprisonment, which in turn allowed him to gain control over Sokar's forces and become a greater threat than before. Heru'ur was seen on the battlefield with his Jaffa as an active general, risking his own life alongside them rather than hiding behind them (as Ra in particular had done). Ba'al was also able to survive the demise of the rest of the System Lords through being infinitely more flexible and adaptable than any of the others had been, even at times allying with SG-1 when he felt the situation warranted it. For a Goa'uld, gender appears to be a matter of choice, or persona, and is not always defined by the Host; one example is Osiris occupying a female body. Goa'uld appear to a certain extent to be able to express and feel love for their mate, or to a lesser extent their children. However, the mating of two Goa'uld host creates a harcesis, an individual who possesses all the knowledge of the Goa'uld. With all the knowledge a harcesis could easily jeopardize the Goa'uld power structure by simply sharing the fact that they are not gods and how their technology worked. For this reason, producing a harcesis was an unspoken taboo among Goa'uld, and if known to exist were hunted down and killed with impunity.

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An infant Goa'uld symbiote emerging from the dead body of a Jaffa Serpent Guard. From the Stargate SG-1 Season 1 premiere episode, "Children of the Gods Part 2".

The Goa'uld first arose in the waters of P3X-888, originally as predators. Eventually, they began taking the native Unas as hosts, becoming more adaptive. They eventually learned how to operate the Stargate the Ancients placed on P3X-888 and left, taking Unas slave armies with them. (SG1: "The First Ones")

Under the leadership of Atok, the Goa'uld developed the first of their society as conquerors, stealing Ancient technology and adapting it to their purposes. In 22,000 BC, Atok was killed by his son Apep, and he reordered the leadership of the Goa'uld. Apep shared power among his underlings, Ra, Nut, and Thoth. However, around 17,800 BC, another Goa'uld began to rise in power: Anubis. Apep's powers began to decline in this time, and Anubis gained more power. Anubis then killed Apep, devouring the symbiote before the eyes of the Goa'uld. However, Ra managed to rally the others in Apep's name. After three centuries of civil war, Anubis was defeated and exiled. Ra organized a new leadership called the High Council of the System Lords. Ra installed himself as the Supreme System Lord of the Goa'uld Empire, and took the Goa'uld QueensHathor and Egeria as mates. (RPG: "Living Gods: Stargate System Lords")

Around 10,500 BC, Ra discovered a healthy world with a primate race: Humans reseeded by the Ancients before they left Earth. Ra took a young native as a host. Revitalized, Ra began allowing the other System Lords access to the Tau'ri. Some were used as worshippers and slaves in Naquadah mines, others were taken to Dakara, and turned into a genetically altered slave-soldier called the Jaffa, to serve as warriors and incubators for larval Goa'uld. A rebellion in 2,995 BC ended Goa'uld dominion on Earth, but Humans had already been seeded throughout the Goa'uld Empire, so Ra felt no need to reconquer the planet. (Stargate) (SG1: "Children of the Gods", "Moebius, Part 1", "Moebius, Part 2")

In 1996, the Tau'ri reopened the Stargate, and sent a team through to Abydos. Ra captured some of them, and found a Nuclear warhead that ColonelJack O'Neill had been given in case he found any threats. Ra enriched the device with Naquadah, and prepared to send it through to Earth, but Dr.Daniel Jackson had told the Abydonians the truth about Ra. They rebelled, and Ra was forced to flee the planet. However, O'Neill and Jackson killed Ra by ringing the primed bomb aboard Ra's vessel as it was taking off, thus evading the orders to destroy the Abydonian Stargate (along with its surrounding population) should the exploration team discover a threat to Earth. (Stargate)

During a mission to find new hosts, the newly created SG-1 met Teal'c of Chulak, Apophis's First Prime who later joined the Tauri and eventually SG-1, Teal'c having long since grown disillusioned with Apophis while still eager to free his people, the Jaffa from slavery at the hands of the Goa'uld.

In the aftermath of a rescue mission, MajorCharles Kawalsky became infected with a Goa'uld symbiote. Attempts to remove it proved unsuccessful with the Goa'uld eventually taking control of Kawalsky's body up until it died after the top of Kawalsky's head was severed while the Stargate was still active. (SG1: "The Enemy Within")

The Replicators soon infested Apophis' mothership, and Apophis took over SG-1's mothership, but it was also infested with Replicators. SG-1 sabotaged the vessel, causing it to crash into Delmak. Apophis was aboard the Ha'tak at the time, and was killed in the crash. As his body was presumably destroyed in the crash, he was killed beyond being resurrected with a Sarcophagus. (SG1: "Enemies")

With the three dominant System Lords dead, the remaining System Lords began a fierce war among themselves to dominate the others. However, they also began to experience a new threat among themselves, as one enemy attacked using only ships, never with Jaffa. The System Lords eventually called the High Council to deal with the issue. The recently returned Osiris also arrived, revealing the identity of their enemy—Anubis. Osiris gave the others two options: restore Anubis to the state of System Lord, or place themselves at the "mercy" of Anubis. Despite the objections of Lord Yu, Anubis was restored to his former status. What they didn't know was that Anubis had achieved Ascension, only to be cast down by the Others. This left him unable to use significant powers, but he still had a great deal of knowledge of Ancient technology. However, Anubis is unable to use any of that knowledge that he would not have been able to know as a Goa'uld. (SG1: "Summit", "Last Stand", "Revelations", "Full Circle")

Eventually, the Replicators began a full scale invasion of the Milky Way, coming into conflict with the Goa'uld Empire. Most of the System Lords such as Yu were killed, with Ba'al being the only apparent survivor. Many among the Rebel Jaffa returned to Ba'al, believing the Replicators to be a "divine punishment". Teal'c and the remaining rebels launched an attack on Dakara, and Jacob Carter discovered that the Dakara superweapon could be used to destroy the Replicators. Jacob, Lt. ColonelSamantha Carter, and Ba'al agreed to reprogram the device, and use it to destroy the Replicators. The plan worked, but the Rebel Jaffa were able to take Ba'al's Ha'tak, forcing him to flee. The remaining Jaffa rebelled en mass. Anubis attempted to retake Dakara, to use the weapon to destroy all life in the Milky Way. However, Oma Desala, who had helped Anubis ascend, chose to battle with him for all eternity. This prevents Oma from helping others to ascend, but also means that Anubis can no longer interfere on the lower planes. (SG1: "Reckoning, Part 1", "Reckoning, Part 2", "Threads")

Bereft of power, and a fugitive of the Free Jaffa Nation, Ba'al fled to Earth, and took control of the Trust. To throw off the Free Jaffa, Ba'al created a series of clones and allowed one of them to be captured and killed by Gerak. Ba'al also attempted to a new plan of conquest: by stealing Stargates and cutting them off from the rest of the network, he intended to activate the Dakara superweapon and destroy all life in the galaxy, causing the Ori, who had recently learned of human life in the Milky Way, to lose interest in the galaxy. SG-1 sabotaged his efforts. (SG1: "Ex Deus Machina", "Stronghold", "Off the Grid")

Hoping to end the Ori invasion, Ba'al captured Adria and took her as a host. He also killed his clones, hoping to cover his tracks. Lt. ColonelCameron Mitchell killed Ba'al during the capture of Adria, and the symbiote placed in her was soon removed. However, Mitchell expressed doubt over whether Ba'al was finally dead, fearing that one or more of Ba'al's clones may have survived. (SG1: "Dominion")

The System Lords under command of Ba'al in the Alternate timeline

Death of the last Ba'al symbiote.

Ultimately, the last of Ba'al's clones was captured and extracted, only for the clone to claim prior to his extraction that the real Ba'al had a contingency plan. Just then, the real one uses a solar flare in conjunction with a Stargate to travel back in time to prevent the Earth Stargate from getting to America by sinking the ship that was taking it to America in 1938, thereby changing the present. Using his knowledge of the future, Ba'al then rose to the highest level in the renewed Goa'uld Empire, bringing a massive fleet to conquer Earth with Qetesh as his queen and Teal'c as his First Prime. Though all of the Systems Lords wished to obliterate Earth from the face of the universe, Ba'al decided to treat them leniently. This got Qetesh suspicious and forced Ba'al to reveal the location of his monitoring base before she killed him. Fortunately, the remaining members of SG-1- who had escaped the alterations to history thanks to them travelling through the Stargate at the moment that history finished changing in the aftermath of Ba'al's modifications- allied with Teal'c and travelled to Ba'al's monitoring base, using the Stargate and a convenient solar flare to send ColonelCameron Mitchell back in time to 1929, allowing him to get into position to be on board the transport ship and kill Ba'al before he destroyed history. With the real Ba'al dead, the extraction went uninterrupted. The Ba'al symbiote died from the extraction while his host survived. With the death of the real Ba'al and his last remaining clone, the last remaining Goa'uld System Lord was dead and the Empire had fallen. (SG1: "Continuum")

A computer scan showing the red colored symbiote within the host body.

The Goa'uld themselves are small snake-like Symbiotes that require a host body. Once they burrowed into body which can be accomplished by piercing the skin in the neck, the parasite begins to wrap itself around the Humanspine. The symbiote then weaves itself around the nervous system where thin filaments are extended that go up into the brain itself. (SG1: "Children of the Gods", "The Enemy Within")

The skeleton of a Goa'uld symbiote.

Once the Goa'uld has taken control of the host body and has become one with it, it possesses the capacity to exert a remarkable level of control over it. This allowed them the capacity to kill the host at will if need be or if they are threatened by others. Standard surgical techniques were proven to be ineffective in removing the symbiote. It is unknown why the Goa'uld which infested MajorCharles Kawalsky could not be removed, after the symbiote was (though it appears there was a piece that was not removed from him, for reasons unknown, which dropped out of his head after he was killed by the Stargate). Even advanced Humans can be susceptible to this as the symbiote can release a deadly poison that can kill the host upon removal. However, the advanced techniques of the Tok'ra allowed them to safely remove a symbiote without causing any permanent physical damage to the host however it is never certain that the symbiont will not release a poison if they try to remove it. This was the case with Adria. (SG1: "The Enemy Within", "Dominion")

Infant Goa'uld that had not reached maturity were not capable of fully taking over a host and only retained control of them for short periods of time which were experienced as black outs by the host. This results in a struggle being fought over the host body between the symbiote and the host itself. In its young state, a symbiote was capable of shedding a dead husk of skin that resembles its body and can make surgeons believe they removed the Goa'uld. (SG1: "The Enemy Within")

The natural form of the Tok'ra queen, Egeria

Mature Goa'uld rearing out of Jaffa's symbiot pouch.

A special class of Goa'uld are the Queens which are responsible for producing new young larval Goa'uld for implantation into Jaffa. When encountering a new tribe of Humans or a different race, the Queen requires to first sample the DNA, or "code of life" as the Goa'uld refer to it, from the species intended to be a host. This is to ensure that there is no rejection during the process between host and larva. (SG1: "Hathor")

One of the unique factors of the Goa'uld race includes their genetic memory which provides each newborn symbiote the collective knowledge of all the Goa'uld that came before it. Another element included within their body's was Naquadah which served as a key to activating their technology and even allowed them to sense the Naquadah present within a Stargate. This does not appear to be a natural aspect of their biology, however, as the early Goa'uld lacked this element within their blood chemistry. (SG1: "The Enemy Within", "Hathor", "The First Ones")

The wild Goa'uld on their homeworld have been shown to cannibalize fellow symbiotes, and also lack Naquadah in their blood. The symbiote is also capable of making its eyes glow in the same way it can with a host. (SG1: "Children of the Gods", "The First Ones")

Within a host, a Goa'uld parasite has complete control, and the degree of control to exert at any given moment is also up to the parasite. Typically entering in through the neck and more seldom through the throat, the Goa'uld will attach itself to the spinal cord which allows access to the brain, leaving an entry mark. When within a host, the Goa'uld gives perfect health, increased strength, and increased intelligence. When in control of the body, the symbiote is capable of making the hosts eyes glow, and also speak in a deep, booming voice. The voice, however, is unnecessary. It may be used to differentiate between parasite and host, as the Tok'ra do, or simply be used to intimidate slaves and opponents. (SG1: "Children of the Gods")

Being taken as a host by a Goa'uld is often considered a terrible fate for the host, as they are suppressed and forced to witness countless horrors. The Goa'uld maintain that the host essentially dies when the Goa'uld takes control, but this has been proven false on numerous occasions. However, a System Lord's lo'taur often considers being taken as a host a "great honor" (they are also around just in case something happens to the host), and indeed even non-Tok'ra Goa'uld and their hosts sometimes coexist willingly (for example Kianna Cyr and possibly Hathor). Certain strong-willed hosts are capable of fighting the control of younger symbiotes that have infested them although only to a marginal extent, such as suppressing a hand movement for a few seconds (SG1: "Children of the Gods", "The Serpent's Lair", "Within the Serpent's Grasp", "Pretense", "Summit", "Last Stand").

The Goa'uld are capable of infesting a wide variety of hosts, from Humans to Unas (which were the Goa'uld's first hosts, because they shared their homeworld with them). They can also take Asgard bodies as hosts for a short period of time, though the Asgard's genetic makeup eventually rejects the symbiote causing the host's body to wither and die. Two species which cannot be taken as hosts are the Ilempiri and Jaffa. (Stargate) (SG1: "Deadman Switch", "The First Ones")

One of the most likely threats a Goa'uld lord can face is being challenged by their children. (SG1: "The Serpent's Lair")

The final wish a Goa'uld can give their First Prime was the task of avenging their death if they were betrayed or killed by a rival. (SG1: "Continuum")

Minor Goa'uld are often forced to serve the more powerful as Underlords and can consist of former warlords that were defeated. While they can serve as lieutenants and commander for the lord in question, there was the danger of the Underlord plotting to overthrow their master. This threat is even greater when one considers, if successful the usurper would gain all the holdings of their master.(SG1: "Prophecy")

The highest authority among the Goa'uld race included the ranks of the System Lords who fielded vast armies under their command as well as warred with one another for dominance. Whenever a System Lord or Minor Goa'uld was vanquished, it was common practice that their domain was absorbed into the victor's ranks. This usually was more than enough incentive for a Goa'uld to go to war with his neighbor and win at all cost.

They make use of personal servants who are normal humans known as Lo'taur that served their every needs. On some occasions, the Lo'taur was used to serve as a spy and gain vital information from the other Lo'taur. An additional benefit of having a Lo'taur is that the Lo'taur can be used as an emergency host. Some Lo'taurs even felt honored by this possibility.(SG1: "Summit")